Homing impulse direction finder



March 25, w41; T. SONNENTAG 2,236,05

HDMING IMPULSE DIRECTION FINDER 'Filed sept. 1o, 193s Patented Mar. 2.5, 1941 UNITEDfsgTATEs nomme IMPULsE plasmon' FINDER.

Theodor Sonnentag, Berlin, Germany', assignor to Telefunken Gesellschaft fr Drahtlose Telegraphie m. b. H., Berlin, Germany, a corpora tion of Germany Application September 10, 1938, Serial No. 229,259 l f En Germany August 28,1937

3 claims. 01. 25o-27) Direction-nndlng by the impulse method, whetherby the aid 'of a Braun tube or by the principle underlying the so-called homing or target-bearing principle, is predicated upon the resolution of the incoming ground -(direct) and space (indirect or sky) wave impulses and the use of receivers designed for wide bands. In what follows a method shall be disclosed,\.whichis adapted to the use of receiver equipmenftdesigned ior narrow bands. f

It is known in the art that ground wave and space" wave impulses may be sorted or separated by utilizing the diierence in time required for the travel or propagation of the electromagnetic waves. For instance, a Braun tube may be used upon the screen of which the patterns or tracings due to the ground wave and the sky wave impulses may be shown separately. In order to allow acoustic direction-hurling by the impulse 0 method, it has been suggested in the earlier art to periodically open and block the receiver at such a rhythm' or rate that only the ground-wave impulses will be registered and indicated. Inasmuch as synchronization for the regulation of thereceiver sensitiveness and response for the incoming impulses is required, it willl be seen that thisv method is unserviceable and unsuited in an impulse-type direction-nuder which operates by the conventional minimum signal method. For thisV v reason, the further suggestion has been made to construct an impulse direction-finder apparatus which is predicated for its operation upon the so-called homing or target-bearing principle. For

, xthislpurpose, a frame antenna and an auxiliary 3g antenna are provided. The input potential oflcne Aoi these two antennae is reversed periodicallyat a certain rhythm or rate.- If visual- (bearing) indication is demanded it is necessary to provide ways and means insuring a change-over or the 40 receiver output circuit acting upon the indicater or reading instrument in synchronism with the .antenna reversals. Periodic opening (unblocking) and blocking of the receiverset is attended `bothwith technical as well as economic disad- The pr'esent invention, therefore, discloses a method ior directionfinding based upon the homing/or target-bearing principle, the outstanding feature of which is that the steepness of slope of iii) the rising portion or stroke of the ground-or direct wave impulse Iis-measured, and that the said slope is utilized ior Va'comparison of the amplitudes oi the ground-wave impulses in the two positions of the diagram.

The inventidn 'will be described by referring'to the accompanying drawings in which Figs. 1 to :iare diagrams vfor illustrating the principle of operation of the invention; Fig. 4 is a schematic circuit diagram of an embodiment of the inven tion; and Fig. 5 is a schematic diagram of the circuit of the invention applied to a homing `impulsl receiver.

The idea underlying the invention is based upon certain facts to be described in more detail byl reference to Figs. 1 to 3. In'the case where the 10 distance between transmitter and receiver is small, ground-wave impulses -B and sky or spacewave impulses R will appear separate in the receiver, as shown in Fig. 1. If the distance is great,

the sky-wave impulse R will reach the receiver 15 at an instant when the received ground-wave impulse B will not have entirely died out. The result willbe a resultant impulse P 'as shown in Fig. 2. I'Ihe rising side 'or up stroke of the ground-wave /impulse B as tar as the point marked a, however, 20

"twill at all events be preserved. Now, since the lslope or steepness of the up-strokes is a measure a'nd criterion for the amplitude oi! the groundwave impulse, it is possible to make comparisons in line with the homing principle by measuring 25f the rising, up-stroke of the ground-wave impulse. The steepness of the-up-stroke of the ground'- wave impulse, forv instance, may be measured by diflerent ways and means.- One method illustrated in Fig. 3 is to measure the time t during 30- 1 -which the -ground-wave impulse passes through two predetermined constant potentials E1 andEz. In. what follows an exempliiled embodiment shall be described by reference to Fig. il in the casewhere the slope of the up-stroke is deter- 'mined by measuring the time t. vAccording to Fig. 4, .the output potentiaisof an'impulse homing receiver lis impressed uponthe grids of two tubes', more particularly Thyratrons 3 and i3. In tite kplate circuit ofthe Thyratron 3 is'in-v 4Q eluded a condenser 3 in parallel relation to a rei j sistance 5, the said condenser il being ycharged through the resistance 1.' Across the terminals of the condenser 9 is connected a voltmeter Il. While the l'I'hyriaitron" 3 discharges in the presence o! a receiver' output potential Ei, the Thyratron I3 should discharge in the presence of Aa d receiver output potential Ez.

` The function of the arrangement is as follows: As stated, the Thyratron" 3 discharges at the instant the up-stroke of the ground-wave impulse attains the voltage level'E1. As a result, a current fiowsthrough the plate circuit of the Thyrtron 3 with the consequence that a constant fall ofpotential arises across the resistance 5. T his fall 65 of potential results in the charging of the condenser 9 according to a curve conditioned by the time-constant of 1, 9. At the instant when the up-stroke of theimpulse has attained voltage E2, Thyratron I3 discharges, and a current is caused to flow in the plate circuit thereof. The voltage arising as a result across the resistance I5 impresses a biasing potential upon the grid of the Thyratron 3 which is oi' sufilcient ampliof the impulse, the instrument deflection is inversely proportional to the amplitude of the ground-wave impulse that happens to be picked up, i

Fig. 5 illustrates the principle of the homing receiver in Awhich has been incorporata?. the circuit organization here disclosed. Such a homing receiver (target-bearing receiver) using impulses comprises a vertical antenna 35 which by the agency of, a reversing switch 36 is connected at will in one sense or`the other with the coil 39 in coupling relation with the receiver equipment. 'Ihe directional or frame aerial 31, through the intermediary of coil 43, is also coupled with the coupling coil 4i ,of the receiver apparatus 45. The voutput of receiver is fed to an -arrangement schematically indicated at l1 which may vcorrespond to an 'arrangement as shown in Fig.

4. [The output terminals of the arrangement 41 adapted to measure the steepness of the slope or up-stroke of the impulse are connected with a change-over or reversing switch 49 which operates in synchronism with the change-over switch 36. It is with this change-over vswitch that the visual indicator or reading instrument is associated.

'Ihe invention is not confined to the use of Thyratron type tubes. As a matter of i'act, other kinds of electronic tubes vmay be employed whose biasing voltageI is altered in a way as hereinbefore illustrated. It is moreover evident that in the impulse homing receiver as shown in Fig. 5 reversal of the frame or loop may be effected in lieu of the reversal of the vertical antenna.

The Vmethod disclosed in the present invention furthermore is not confined to impulse directionfinding systems working on the target-bearing or homing principle. In fact, as a general rule, it is suited for a measurement or for a comparison of radio impulses. Comparisons ofthis kind may be required, for instance, whenever it is necessary to ascertain or' read distances from the intensity of incoming radio impulses.

I claim as my invention:

1. 'I'he method of visually indicating the reception of an impulse from an impulse type of transmitter which includes initiating an electrical discharge when said received impulse reaches a predetermined amplitude, initiating a second electrical discharge when said received impulse reaches a second predetermined amplitude, extinguishing said first discharge by application of said second discharge, and indicating the time between said predetermined amplitudes.

2. 'I'he method of visually indicating the reception of an impulse from an impulse type of transmitter which includes initiating an electrical.

discharge' when said received impulse reaches a predetermined amplitude, stopping said discharge when said impulse reaches a second pre- 3.

determined amplitude, deriving a voltage the amplitude of which is a function of the time ibetween the occurrence of said predetermined amplitudes, and observing the amplitude of said voltage.

3. The method of visually indicating the reception of an impulse from an impulse type of transmitter which includes initiating anfelectrical discharge when said received impulse reaches a predetermined amplitude, initiating a second discharge when said impulse reaches a second predetermined amplitude applying said second discharge to extinguish saidk first discharge,

-deriving'a voltage the amplitude of which is a function of the time between the occurrence of said predetermined amplitudes, and observing the amplitude of said voltage.

THEoDoR SONNENTAG. 

